If you're building or sourcing power tool battery packs, you already know the lithium-ion battery cell inside that pack decides everything — from run time and safety to whether your product can even ship to the US or EU. At Highstar, we've spent over 30 years making cells that pass the toughest certification tests. Here's what you need to know.

What Is a Lithium-Ion Battery Cell?

Let's start at the ground level. A lithium-ion battery cell is the basic unit that stores and releases energy using lithium-ion movement between a positive (cathode) and negative (anode) electrode. Multiple cells form a module, and several modules create a battery pack. When you pick up a cordless drill or an impact driver, the battery pack clipped onto the base is made up of individual lithium-ion cells wired together in series and parallel configurations. Those cells are doing all the heavy lifting.

Lithium-ion cells are manufactured in multiple form factors, including cylindrical (like 18650 and 21700), prismatic, and pouch cells. For power tools, cylindrical cells — especially 18650 and 21700 formats — are the go-to. Various rechargeable Li chemistries dominate, and battery management systems (BMS) are critical in cordless tool packs. At Highstar, we produce both NMC cylindrical cells and LFP prismatic cells. Our 21700 lineup, for example, delivers energy densities up to 295 Wh/kg and can handle discharge rates up to 60A continuous, making them perfect for high-drain applications like power tools and electric vehicles. If you want to dig deeper into LFP options and who makes them, check out our list of top LFP battery cell manufacturers.

The chemistry you pick — NMC, NCA, or LFP — shapes your pack's voltage, energy density, cycle life, and thermal behavior. Different lithium battery chemistries offer varying performance characteristics, cycle life, and safety features. NMC cells give you higher energy density in a smaller package, which is why most premium power tool brands use them. LFP cells are tougher and safer but heavier per watt-hour. Lithium-ion cells provide energy densities of 240–270 watt-hours per kilogram, while LiFePO4 cells offer enhanced safety margins and cycle life performance exceeding 1000 charge cycles, though at reduced energy density compared to standard lithium-ion chemistries. Your choice of cell directly shapes the certification path your pack will follow, so get this right early in the design process.

UL Certification for Lithium-Ion Cells Explained

If you want to sell a power tool battery pack in the United States, UL certification is where it all starts. UL certification is a critical safety access requirement for battery products in the U.S. market, particularly for batteries used in energy storage, consumer electronics, power tools, and other fields. While technically a voluntary certification, it has practically become a trusted safety credential among consumers, retailers, and even regulatory authorities. Big retailers, Amazon, and professional buyers won't touch a product without that UL mark. And if you're shipping lithium-ion cells or packs, the entire supply chain — from warehouse to end user — expects proof that your batteries are safe.

There are several UL standards that apply to lithium-ion battery cells and packs, and they layer on top of each other. UL1642 is a battery safety standard developed by Underwriters Laboratories (UL) that evaluates the safety of lithium cells used in electronic products and industrial systems. UL1642 focuses specifically on cell-level safety, which means it evaluates individual battery cells rather than complete battery packs. Think of it as the foundation. UL 1642 is the foundation for battery pack certification. Once your cells pass UL 1642, you move up to pack-level standards. UL 2054 is the most widely used standard for household and commercial battery packs. For power tools specifically, you'll also deal with IEC/UL 62841-1, the Standard for Safety for Electric Motor-Operated Hand-Held Tools. And every lithium-ion battery — every single one — must be tested to UN 38.3 prior to shipping.

At Highstar, safety testing covers the national standard GB31241, North American UL1642, UL1973 standards, the International Electrotechnical Commission IEC62619 standards, Japan PSE, India BIS, South Korea KC, and other major economies' lithium battery safety testing standards. We don't leave certification to chance. We have professional testing laboratories that cover the entire lithium battery industry chain (including cell materials, cells, electronics, PCM, and PACK) and TÜV-certified safety laboratories. That means when you source cells from us, the groundwork for your UL certification is already done. You get documented test data, traceable cell performance records, and engineering support to help you move through the certification process without delays.

CE Marking and IEC Standards for EU Market Access

Selling your power tool battery pack in Europe means you need the CE mark. CE certification shows that a product follows European Union (EU) safety and environmental rules. For lithium batteries, it ensures they are safe, eco-friendly, and work well with other devices. Companies need CE certification to sell products in the EU. Unlike UL, which is third-party tested and audited, CE marking can sometimes involve self-declaration. But for lithium-ion battery packs — especially in power tool applications — you're usually going through rigorous testing to IEC standards anyway.

The backbone of CE compliance for batteries is the IEC 62133 standard. IEC 62133 is the safety requirement for testing secondary cells and batteries containing alkaline or non-acid electrolytes. This standard covers both nickel and lithium battery chemistries, making it broader in scope compared to UL 1642. The standard is divided into two parts, with Part 1 focusing on nickel-based batteries and Part 2 on lithium-ion and lithium polymer batteries. For power tool packs, Part 2 (IEC 62133-2) is the one you care about. It tests for overcharge, short circuit, forced discharge, vibration, thermal misuse, and more — all at the pack and cell level. EN standards form the basis for CE marking, mandatory for EU market access.

Here's something worth knowing: IEC 62133 and UL 1642 test a lot of the same failure scenarios. Two of the most prominent safety standards in the battery industry are UL 1642 and IEC 62133. Though both serve the same fundamental purpose of ensuring the safe operation of batteries, there are key differences in their scope and application. UL 1642 is widely recognized in North America and often considered a benchmark for battery safety in consumer electronics, while compliance with IEC 62133 is often required for products entering international markets, as it is recognized by multiple countries. If you plan to sell in both the US and Europe — which most power tool brands do — you'll need both. The good news is that many test labs run both protocols side by side, and starting with UL 1642-certified cells saves you time and money on the IEC side. At Highstar, our cells are tested to cover both North American and international safety requirements, so your path to dual-market compliance is smoother from the start.

Key Safety Tests for Power Tool Battery Packs

Power tool battery packs get pushed harder than almost any other consumer lithium-ion product. Unlike consumer electronics, power tools operate under high current loads, frequent charge–discharge cycles, and continuous heavy-duty usage, often generating significant heat. That's exactly why certification tests are so intense. Here's a look at what your lithium-ion battery cells and packs will go through.

The UL1642 standard defines safety requirements and abuse tests for lithium battery cells to reduce risks such as thermal runaway, fire, or explosion. The tests simulate the worst-case scenarios your cells might face in the real world. UL 1642 concentrates on safety tests designed to evaluate the cell's response to abnormal conditions, including tests for thermal abuse, mechanical shock, and impact resistance. The emphasis is on preventing thermal runaway and ensuring the cell does not pose a risk of fire or explosion.

Here's a quick reference table of the main tests your cells and packs need to pass:

These aren't boxes you check once and forget. Prior to issuing certification, UL performs a Factory Inspection Audit (FIA) to ensure that the production processes align with the tested samples. After certification, audits are conducted quarterly or biannually to retain the UL Mark. That's why picking a cell supplier with a strong quality system matters so much. If the cells change even slightly between your certification samples and production batches, you'll fail the audit. At Highstar, our fully automated production lines and in-house testing labs keep cell-to-cell consistency tight, so what you certify is what you ship.

How to Choose the Right Cell for Your Power Tool Pack

Picking the right lithium-ion battery cell for a power tool pack isn't just about grabbing the cheapest option. You need a cell that can handle high-rate discharge, stay cool under load, and survive thousands of charge cycles without falling apart. To deliver consistent torque and performance, batteries must sustain large continuous currents without voltage drops. Here's how we recommend approaching it.

Start with your discharge needs. Power tools pull massive amounts of current compared to a phone or laptop. Tests show high-rate 18650 cells maintaining 20–25A continuous discharge for over 500 cycles provide optimal performance for most cordless drills and impact drivers. If you're building packs for heavier equipment like circular saws or rotary hammers, you'll want 21700 cells for the extra headroom. Our Highstar 21700 Tabless Cell series, for example, supports 40C pulse discharge (200A) and 70A continuous discharge, enabling smooth operation for high-intensity tools like electric drills and saws. That's the kind of real-world performance that separates a pro-grade pack from a budget one.

Next, think about cycle life and thermal stability. Cycle life refers to the number of charge–discharge cycles a battery can undergo before its capacity significantly diminishes. For power tools that get used daily on a job site, anything under 500 cycles is a non-starter. A high-quality lithium-ion power tool battery typically maintains 70–80% of its original capacity after 500 to 800 charge cycles. Lithium-ion batteries are happiest when their state-of-charge is kept between 40% and 80%. Heat is the silent killer of lithium-ion cells. If your pack design doesn't account for thermal management during high-drain use, even the best cell in the world will degrade fast. That's why cell-level thermal stability and low internal resistance matter just as much as raw capacity numbers.

Finally, think about certifications and traceability from day one. Ensure the batteries have necessary certifications like UN 38.3, UL 1642, and CE marking. Don't wait until your pack design is finalized to check whether your cells can pass UL 1642 or IEC 62133. If a manufacturer can't show you their UL, IEC, or UN38.3 certifications, that's a red flag. Work with a cell manufacturer who has the test reports ready, who runs automated lines with batch traceability, and who can provide the technical documentation your certification lab will ask for. At Highstar, we've shipped over 4.5 billion cells globally since 1994, and our engineering team works directly with OEMs to make sure cell selection, pack design, and certification all line up from the start. We offer custom BMS design, appearance mold engineering, and safety certification support — so you're not juggling multiple vendors when deadlines get tight.

Certification Costs and Timelines

One of the first questions we hear from customers is, "How much does it cost and how long does it take?" Fair question. The answer depends on how many standards you need to hit and how ready your cells and pack design are.

UL Certification typically ranges from $15,000 to $20,000. UL Certification typically takes around 10 to 12 weeks. That's for a standard process — if your cells already hold UL 1642, the pack-level certification (UL 2054 or the applicable tool standard) moves faster because you're not retesting at the cell level. IEC Certification is estimated between $6,000 and $10,000, and usually requires 6 to 8 weeks. UN38.3 Certification usually costs between $5,000 and $7,000. Keep in mind that these numbers can shift based on how many samples you need, whether redesigns come up during testing, and which lab you use.

The biggest cost savings come from getting things right before you walk into the lab. That means using cells with existing UL 1642 certification, designing your BMS to meet the overcharge and over-discharge protection limits upfront, and having all your technical documentation — cell spec sheets, circuit diagrams, bill of materials — organized before you submit samples. Products which use lithium-ion batteries pose a considerable risk of overheating, fire, or chemical leakage during abnormal situations. The certification process exists to catch those risks early. When your cells are already proven and your pack design follows best practices, you avoid the costly cycle of test-fail-redesign-retest that eats up budgets and delays product launches.

FAQs

What is UL 1642 certification and do I need it for power tool battery cells?

UL1642 is a safety standard for lithium battery cells, focusing on abuse testing and construction safety. Any company making or using lithium cells in products such as phones, laptops, power tools, medical devices, or wearables should consider UL 1642 certification. If you want to sell your power tool battery pack in the US — especially through major retailers or Amazon — you need it. Most UL standards for finished products explicitly require the incorporated cells to hold UL 1642 certification.

What is the difference between UL 1642 and UL 2054?

UL 1642 ensures the safety of lithium cells themselves, while UL 2054 ensures safety of the whole battery pack. UL1642 applies to battery cells only, while UL2054 applies to battery packs only. The two are in a prerequisite and subsequent relationship and cannot be substituted for each other. For a power tool battery, you typically need both — UL 1642 on the cells, and the relevant pack-level standard on the assembled battery.

Can I sell lithium-ion battery packs in Europe without CE marking?

No. Companies need CE certification to sell products in the EU. The CE mark is important for electronics and industrial tools. It proves the product passed strict tests and meets EU rules. For lithium-ion packs, CE compliance usually means testing to IEC 62133-2 plus relevant EMC and environmental directives (like RoHS and REACH).

What certifications does Highstar hold for its lithium-ion battery cells?

At Highstar, safety testing covers the national standard GB31241, North American UL1642, UL1973 standards, the International Electrotechnical Commission IEC62619 standards, Japan PSE, India BIS, South Korea KC, and other major economies' lithium battery safety testing standards. We also have TÜV-certified safety labs and run testing across the full battery industry chain — from raw cell materials all the way through finished packs.

How does cell chemistry affect battery pack certification?

Factors like cell type, materials, casing, BMS, and sealing impact tests for pressure resistance, impact resistance, IP rating, and thermal propagation. Test data indicates that NCA and LCO chemistries generate higher flame speeds during thermal events compared to LFP chemistry, directly influencing the scope of safety testing requirements. In short, your choice of NMC, NCA, or LFP cells changes which tests get more scrutiny and how your BMS protection logic needs to be designed. Get your cell chemistry locked down early, and your certification path gets a lot clearer.

Ready to build a power tool battery pack that passes UL and CE with confidence? Talk to our team at Highstar. We'll help you pick the right lithium-ion battery cell, design your pack, and get through certification — all under one roof.